Patterning Macromolecules And Microcapsules By Soft Lithography

Surface microfabrication is an important way in realizing materials function. It is also a key technique in modern science and engineering. This paper focuses on the surface patterning by soft lithography, one of the most useful patterning techniques at present.Firstly the poly(dimethylsiloxane) (PDMS) elastomeric stamp used in soft lithography was fabricated by the photolithography technique. Then, serial active surfaces such as amino-silanized glass slide or aminolyzed polycaprolactone (PCL), poly(L-lactic acid) (PLLA) and poly(ethylene terephthalate) (PET) were prepared. After investigating the characteristics of microcontact printing technique and biomacromolecules, a novel inking process named "coating, drying, and condensation" was used in reactive microcontact printing biomacromolecules such as bovine serum albumin (BSA). A notable feature of this process is that the biomacromolecule solution can be inked on the stamp at a controlled state, neither too "dry" nor too "wet". It not only ensured the high interface reaction activity between the biomacromolecules and the activated substrate, but also enhanced the BSA transferring efficiency, thus forming patterns with high contrast, while avoiding the contamination caused by dispersal of excessive solvent. The same clear patterns of BSA were also obtained by pressing a condensed stamp, which was selectively filled with biomacromolecules in its microwells beforehand, onto an aldehyde-enriched surface. The notable feature of this process is that the reaction between the biomacromolecules and the active surface could be performed at a comparable speed to that in solutions, thus resulting in higher contrast and good stable patterns.Based on the requirement of more accurate control of cell attachment, co-patterning of two types of biomacromolecules that have opposite effect on cell adhesion was realized by a modified microcontact printing technique named "side by side" process. Briefly, one kinds of biomacromolecule such as chitosan was firstly microcontactprinted onto an active surface, followed by adding a drop of albumin solution and holding for a while. After washed and cleaned by rinse and ultrasonic, the co-patterns of chitosan and albumin, each with their own micropatterns, were formed on the same surface. In this procedure, ultrasonic cleaning takes an important role to obtain clear patterns, whereas the printing/adding sequence has less influence.Another process developed for co-patterning biomacromolecules is "top on top". Briefly, the negatively charged BSA was adsorbed firstly onto a positively charged surface such as amino-enriched surface, then a positively charged chitosan layer was stamped onto the BSA layer. Confocal laser scanning microscopy visualized the clear co-patterns. It was found that rinsing the BSA-adsorbed substrate and the chitosan-inked stamp before microcontact printing is crucial for creation of clear and stable co-patterns. As the electrostatic interaction between chitosan and BSA is nonspecific, this process could be generally applied to pattern other biomacromolecules.Polyethylene glycols (PEG) is an effective molecule to resist biomacromolecule adsorption. PEG patterns can induce biomacromolecule patterning. In this paper, amino-ended PEG was first synthesized via hydroxyl group activation technique. Its covalently patterning was realized by two methods, e.g. direct reactive microcontact printing and microtransfer patterning. Subsequent immersion of these PEG patterned surfaces into biomacromolecule solutions such as BSA or chitosan realized biomacromolecules patterning. The higher BSA pattern contrast implies that microtransfer patterning is a more effective way in realizing PEG patterning due to the higher reaction activity.Polyelectrolytes patterning could greatly enlarge their application range. In this paper, polydiallyldimethylammonium chloride (PDAC) was microcontact printed onto the PDAC/poly-(styrenesulfonate) (PSS) multilayers with PSS as the top layer. In this process, clear chemical-co-physical patterns we...